RE: Flying wing gliding in high winds
My first concern would be having a radio with the range to control the plane (or did you say you have on board autopilot?)
When Maynard Hill was setting altitude records in the 70s, he used a directional antenna on ham freqs (I believe)
If you pick your weather days carefully, you can have a flight to 35K with little to no wind drift. With a high pressure ridge practically over your head, you could get to 100K with as little at 4 miles of drift. I launch weather balloons for a living (NWS) and I have had many flights where the winds reverse above the tropopause (about 40K) and the balloon drifts back over the station. I once tracked a balloon to landing less than 4 miles away with a flight to 102K.
Good luck!
Don